(a) Field of the Invention
The present invention relates to a method for welding a structure, and more particularly, the present invention relates to a method for welding a hollow structure.
(b) Description of the Related Art
Friction stir welding was developed by TWI in the United Kingdom in 1991. Friction stir welding is a solid-state welding process that uses frictional heat and a plastic flow phenomenon that occurs when inserting a rotating tool into a material to be welded. The sold-state welding process is applied to weld a variety of light metals because, compared to fusion welding process, a solid-state welding process induces low distortion to materials. Due to the above merit, Hitachi in Japan uses a friction welding process to fabricate the frames of railway vehicles, instead of using metal inert gas (MIG) welding.
However, when friction stir welding is used to weld a material, a high load is applied to the material because friction welding is a kind of mechanical welding process. For this reason, there is problem that when designing a shape to be welded, a rib needs to be inserted to support a load and thus designing a shape to be welded is complicated, and the shapes of extrusion tools for extrusion are complex.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.